Mild temperatures were also expected tomorrow - a high of 20C is forecast in Tauranga, 19C in Auckland, Whāngārei, Napier and Dunedin, and 18C in Hamilton and Christchurch.
Wellington will be a cool 16C and Palmerston North 17C.
Meanwhile, today would start cool for inland parts of the country - Waiōuru and Taumarunui were forecast 0C overnight lows and Taupō only marginally higher with 1C.
Frosts were expected for the the "usual inland suspects" - such as Waikato, the central North Island, Canterbury high country and Central Otago, Makgabutlane said.
Fine weather is forecast for most, there may be some cloud on the western side of the North Island between Taranaki and Kapiti Coast.
Daytime temperatures would be average for the time of year - mid to upper teens for most, although eastern Canterbury could be above average, with 21C forecast.
While warmer than average, don't expect a hot day, Makgabutlane said.
"We're still in May."
The next wet weather system isn't too far away, but only for some, she said.
It would begin arriving on Tuesday for the western and southern part of the South Island, but other parts of the country could expect the fine weather to continue.